1. Field of the Invention
This invention relates generally to semiconductor process equipment, and more particularly, to an air bearing and seal and method of using the same.
2. Description of the Related Art
Semiconductor processing typically involved the formation of one or more layers on a semiconductor substrate. As those of skill in the art understand, it was critical to avoid particulate contamination of the formed layers.
Disadvantageously, mechanical bearings employed with the semiconductor processing equipment were a primary source of particulate generation and contamination. For example, when the mechanical bearing was a ball bearing, friction on the balls of the bearing generated particulates.
For this reason, air bearings were frequently employed. An air bearing used a layer of gas between moving parts thus avoiding particulate generation from friction between the parts. Although reducing particulate generation compared to a mechanical bearing, as discussed in greater detail below with reference FIGS. 1 and 2, an air bearing was still a significant source of particulate generation and contamination.
FIG. 1 is a perspective view of an air bearing 10 in accordance with the prior art. FIG. 2 is a cross-sectional view of air bearing 10 of FIG. 1 along the line IIxe2x80x94II. Referring now to FIGS. 1 and 2 together, air bearing 10 included a rectangular slide 12 and an air bearing body 14. Pressurized gas, e.g., air or nitrogen, indicated as arrow 16, was supplied to air bearing body 14 through a pressurized gas port 18. This pressurized gas passed through a channel in air bearing body 14 and was supplied at the interface of slide 12 and air bearing body 14, hereinafter called an air bearing region 20.
Due to this pressurized gas, slide 12 floated on air bearing body 14. Stated another way, a layer of gas, sometimes called an air bearing, was located between slide 12 and air bearing body 14. Accordingly, slide 12 moved on a layer of gas thus avoiding particulate generation due to friction between slide 12 and air bearing body 14.
To maintain the air bearing, pressurized gas was continuously supplied to air bearing region 20. This pressurized gas continuously escaped from air bearing region 20 into a clean area 30 as indicated by arrows 22. Clean area 30 was an area in which particulates were undesirable, e.g., an area in which silicon wafers or other substrates were handled.
Although great care was taken to supply only the highest purity pressurized gas, the pressurized gas inherently contained particulates. As the pressurized gas escaped from air bearing region 20 into clean area 30, the particulates contained within the pressurized gas also escaped from air bearing region 20 into clean area 30. These particulates were a significant source of particulate contamination of clean area 30.
Further, as the pressurized gas escaped from air bearing region 20, the pressurized gas had a tendency to dislodge and move about particulates within the vicinity of air bearing 10 in clean area 30. This also was a significant source of particulate contamination of clean area 30.
In accordance with the present invention, a particulate free air bearing and seal is formed between a slide and an air bearing body. Pressurized gas is supplied to an air bearing region between a first air bearing surface of the slide and a second air bearing surface of the air bearing body. The pressurized gas is supplied to the air bearing region through a distributor in the second air bearing surface of the air bearing body. The pressurized gas causes the slide to float on the air bearing body avoiding particulate generation due to friction between the slide and the air bearing body.
As pressurized gas is supplied to the air bearing region, vacuum is simultaneously supplied to a collector also in the second air bearing surface of the air bearing body. The collector captures the pressurized gas escaping from the air bearing region and prevents the pressurized gas from entering a clean area.
Since the pressurized gas from the air bearing region is prevented from entering the clean area, any possibility of particulate contamination of the clean area from particulates entrained within the pressurized gas is eliminated.
This is in contrast to a prior art air bearing where the pressurized gas, which escaped from the air bearing region, entrained particulates into the clean area within the vicinity of the air bearing. These particulates were a significant source of particulate contamination in the prior art.
Further, since the pressurized gas escaping from the air bearing region is prevented from entering the clean area, any possibility of the pressurized gas dislodging and moving about particulates within the clean area is eliminated. This is in contrast to a prior art air bearing where the pressurized gas, which escaped from the air bearing region into the clean area, had a tendency to dislodge and move about particulates in the clean area. These particulates were also a significant source of particulate contamination in the prior art.
In an alternative embodiment, the slide and the air bearing body are stationary and do not move with respect to one another or, alternatively, move on mechanical bearings between the slide and the air bearing body. In accordance with this embodiment, the air bearing functions as a seal instead of as an air bearing. The air bearing prevents particulates from passing between the air bearing body and the slide.
Since the air bearing region is supplied with pressurized gas from the distributor, the air bearing region is at a higher pressure than areas adjacent the air bearing region (the adjacent areas), e.g., the air bearing is between the clean area and a dirty area in which motors are located. Thus, any leakage of gas is pressurized gas leakage from the air bearing region into the adjacent areas and not vice versa. This prevents gas and particulates in the adjacent areas from entering into the air bearing region.
Further, even if gas and particulates do enter the air bearing region, the gas and particulates are captured by the collector and prevented from escaping from the air bearing region. In the above manner, the air bearing forms a seal between the air bearing body and the slide.
In one embodiment, the air bearing body is a tabletop, which remains stationary. The slide is a robot pedestal, which rotates and moves upwards and downwards during substrate handling. An air bearing between the tabletop and the robot pedestal forms a seal which prevents particulates from escaping between the tabletop and the robot pedestal as the robot pedestal moves.
In another embodiment, a robot arm includes a slide and an end effector arm mounted to the slide. The slide is supported on a hanger. An air bearing between the slide and the hanger allows the slide to freely move on the hanger along a linear axis of the robot arm. Advantageously, the slide moves on the hanger without generating any particulates.
The slide has a base, which has a first surface. A vacuum coupler trench and a pressurized gas coupler trench are in the first surface of the base. The hanger has a vacuum channel and a pressurized gas channel. The vacuum channel extends to a first aperture in a lower surface of the hanger. The first aperture is aligned with the vacuum coupler trench. The pressurized gas channel extends to a second aperture in the lower surface of the hanger. The second aperture is aligned with the pressurized gas coupler trench.
The pressurized gas coupler trench is coupled to a distributor in an air bearing surface of the slide. During use, pressurized gas is supplied through the pressurized gas channel in the hanger to the pressurized gas coupler trench of the slide. The pressurized gas is supplied from the pressurized gas coupler trench to the distributor, thus forming the air bearing between the slide and the hanger.
Of importance, the entire periphery of the air bearing surface of the slide is lined with a collector. The collector is coupled to the vacuum coupler trench. Vacuum is supplied through the vacuum channel in the hanger to the vacuum coupler trench of the slide. The vacuum is supplied from the vacuum coupler trench to the collector.
Advantageously, pressurized gas from the distributor is captured by the collector. Thus, any particulates entrained within the pressurized gas do not escape into the vicinity of the slide, e.g., into a clean area in which substrates are handled.
These and other features and advantages of the present invention will be more readily apparent from the detailed description set forth below taken in conjunction with the accompanying drawings.